php.ini variable preventing fopen() - filesize() - fclose() functions?

This is a openscript php code verification script that prevents auto entry where a human views alpha-numeric text and then types in what they see.

Works on different server, not the one copied to hence wondering if php.ini variables are the cause.

Url = http://americas-original.com/simg.php

Code =


<?php

/***************************************************************************
 *                            Dolphin Web Community Software
 *                              -------------------
 *     begin                : Mon Mar 23 2006
 *     copyright            : (C) 2006 BoonEx Group
 *     website              : http://www.boonex.com
 *
 *    
 *
 ****************************************************************************/

/***************************************************************************
 *
 *   This is a free software; you can modify it under the terms of BoonEx
 *   Product License Agreement published on BoonEx site at http://www.boonex.com/downloads/license.pdf
 *   You may not however distribute it for free or/and a fee.
 *   This notice may not be removed from the source code. You may not also remove any other visible
 *   reference and links to BoonEx Group as provided in source code.
 *
 ***************************************************************************/

require_once( "images.inc.php" );

ob_start();
session_start();
$chars = array("a","A","b","B","c","C","d","D","e","E","f","F","g","G","h","H","i","I","j","J",
                     "k","K","L","m","M","n","N","o","p","P","q","Q","r","R","s","S","t","T",
                     "u","U","v","V","w","W","x","X","y","Y","z","Z","2","3","4","5","6","7","8","9");
$textstr = '';
for ($i = 0, $length = 5; $i < $length; $i++) {
   $textstr .= $chars[rand(0, count($chars) - 1)];
}
$hashtext = md5($textstr);

$_SESSION['strSec'] = $hashtext;


if ( produceSecurityImage( $textstr, $hashtext ) != IMAGE_ERROR_SUCCESS )
{
      // output header
      header( "Content-Type: image/gif" );
      
      // output error image
      $errorFilename = $ID_PIC_DIR . 'simg_error.gif';
      $fp = fopen( $errorFilename, 'r' );
      $fsize = filesize( $errorFilename );
      if ( $fp )
      {
            print fread( $fp, $fsize );
      }
      fclose( $fp );
}

ob_end_flush();
?>